1. Field of the Invention
The present invention relates to methods for mounting an end piece member on an open end of a thin-walled hollow tube member without inducing radial distortion of the hollow tube member, particularly in the assembly of photoreceptor drums or the like.
2. Description of the Prior Art
Reprographic devices, such as photocopiers, duplicators, and laser printers, commonly utilize electrostatic principles to reproduce printed materials. In operation, the image to be printed is generated onto a substrate, such as a rotatable photoreceptor drum, by an electrographic process. Toner or developer material is then applied to the substrate to create the image in visible form, which then is transferred and fixed to paper or similar base material.
Recent advancements in reprographic techniques have resulted in greatly enhanced imaging definition. However, these results are dependent upon the high dimensional accuracy and interaction of the various components which make up the reprographic device. In particular, even minute variations in the rotational alignment or surface evenness of the photoreceptor drum can prove detrimental to the image generation process, making efforts toward improving image resolution futile. As such, the dimensional accuracy of the photoreceptor drum is critical to the achievement of the desired imaging definition. The primary indicator of dimensional accuracy of the photoreceptor drum is referred to as Total Indicator Run-out (TIR), which is a measure of the trueness of the drum surface and the centricity of the rotational axis.
To date, a photoreceptor drum or the like, is typically assembled by frictionally fitting and securing at least one end piece member into an open end of a hollow tube member. The hollow tube member is typically made of, but not limited to, aluminum, or any other conductive material, which is then specially treated with successive layers of extremely sensitive semi- and photo-conductive solutions. The end piece member includes a central aperture to receive a central axial shaft for rotatably supporting the hollow tube member. As such, the hollow tube member must be precision manufactured to include a mounting area to snugly receive the end piece member concentrically therein, while inducing minimal radial distortion to the outer peripheral surface of the hollow tube member.
The precision manufacture of the hollow tube member and end piece member includes cutting the tube member to the proper length; machining a mounting area into the open end of the tube; truing the exterior surface of the tube member; and machining the end piece member to be concentrically received by the corresponding mounting area. However, since the hollow tube member must be constrained during a majority of the manufacturing process, distortion of the manufactured tube member inherently occurs when the constraints are removed and the tube member returns to its unstressed, relaxed condition.
Further distortion of the exterior surface of the hollow tube member occurs upon insertion of the end piece member into the mounting area, due to the snug frictional engagement and tolerance stack-up between the end piece member and the mounting area of the hollow tube member, as seen in FIG. 1. Of course, concerns over dimensional inaccuracies are not limited to the distortion of the substrate surface. Tolerance stack-up between the end piece member and the hollow tube member inherently results in eccentric alignment of the end piece member, as well.
An additional consideration in the manufacture of photoreceptor drums is cost of production. The precision machining processes typically required for the hollow tube member and end piece member add extraordinary expenses to the overall assembly cost of the photoreceptor drum. Likewise, while a thin-walled hollow tube member is preferred for economic reasons, the current method of assembling a photoreceptor drum prohibits its use since the thin-walled member cannot be adequately machined to include an end piece member mounting area.